Annular knife.



No. 877,927. PATENTED FEB. 4, 1908 -E. G. HOFPMANN.

ANNULAE KNIFE.

APPLICATION FILED MAY 14, 1907.

I 2 SHEETS-SHEET 1.

WITNESSES INVENTOH I 5w (am/4 M ATT HNEYS No. 877,927. PATENTED FEB. 4, 1908.

E. G. HOFPMANN. ANNULAR KNIFE.

APPLICATION FILED MAY 14, 1907.

2 SHEETS-SHEET Z.

WITNESSES 6 I I JW- wlkM/NVENTOL A77 HNEYS ERNST GUSTAV HOFFMANN, OF NEW ROCHELLE, NEW YORK.

ANNULAR 1m IFE.

Specification of Letters Patent.

Application filed May 14' 1907- Serial No. 373-592- Patented Feb. 4,1908.

To all whom it may concern:

Be it known that I, ERNST GUSTAV CHOFFMANN, a citizen of the United States,

residing in the city of New Rochelle, in the county of Westchester, in the State of New York, have invented certain new and useful Improvements in Annular Knives, of which the following is a specification, reference being had to the accompanying drawings, forming a part hereof.

Machines of certain kinds, such as leather skiving machines, are equipped with annular knives which are rotated at high speed. The

conditions under which such machines are operated require the knives not only to be accurately balanced, because of the high speed at which they are driven, but also require the knife to have a practically smooth exterior, free from projections of any kind, and also to have a smooth interior, also free from projections and so shaped as tov discharge readily that portion of the material operated upon which is projected within them. To produce such knives of suitable temper and approximating the desired degree of perfection in the other respects noted, is a matter of much expense, partly by reason 'of the skill and amount of time required to make the knives ready for use, and partly by reason of the weight of material required, which is itself objectionable, not only because of the amount ofmachining necessary, but also because of the weight of the knife when completed.

It is the object of this invention to produce knives of the character referred to which shall be better adapted for their intended use than the knives heretofore produced and can be. produced at much lessexpense.

In accordance with this invention the cutting portion or blade of the knife is made in cylindrical form of high grade steel, preferably by butt-welding the ends of a band.

complete kmfe.

with respect to the base.

The invention will be more fully explained hereinafter with reference to the accompanying drawings in which Figure 1 is -a view in axial section' of the improved knife made as hereinafter described. Fig. 2 is a view similar to Fig. 1 but showing the base and blade separated and in readiness to be united. Fig. 3 is an edge view of the base portion of the knife in readiness to have the blade secured thereto. Fig. 4 is a view similar to Fig. 1 but showing the base and blade united differently. Fig. 5 is a View similar to Fig. 4 and illustrating the manner of uniting the two parts with a knife. Fig. 6 is an edge view of the knife also illustrating the manner of uniting the parts.

In the form of the improved knife shown in Figs. 1, 2 and 3, the cup-shaped base or body a is formed by stamping up into proper shape a sheet of soft steel and along its outer edge it is provided with a series of isolated welding points a, distributed at intervals about the circumference, such welding points being formed in any suitable manner, as by laying on small bits of metal or, as shown in the drawings, by pinching the metal of the body to form such points.

The annular blade I; is separately formed of high grade steel adapted for the purpose to which the knife is to be put, preferably by coiling into a ring a strip of metal of suitable len th and width. The blade is also preferabFy formed about its inner edge with a series of projections or recesses, as may be convenient, distributed about the circumference in correspondence with the points a, of the base and cooperating therewith so as to insure the accurate placing of the blade I The two parts of the knife are then assembled and securely united by Welding at such isolated points, distributed at intervals about the circumference. In this manner the necessary strength o union between the parts is secured without drawing the temper of the blade or otherwise aflecting injuriously any portion of the knife. The welding is conveniently effected electrically.

- After the parts of the knife are assembled and united, as described, the blade is ground true, inside and outside, in the usual manner,

so that it forms a continuous and unbroken Figs. 4, and 6.

' the. two

cuttings ofthe material operated u on by the knife, which are projected wit in the knife, are permitted to 'WOIk themselves freely out of the way, such action being facilitated by the well rounded internal shoulder of the stamped steel bottom.

- no abrupt shoulder within the knife. The

two parts, when thus formed and assembled, are integrally united, as by welding at isolated' points or intervals, preferably by an electrical welding machine, in which one of the conducting contacts, as c, is formed to fit snug y within the edge of the base or body portion, whilev the other conducting contact (1, of limited area at the point of contact as shown in Figs. 5 and 6, is applied externally to the lapping portions of the two parts at isolated points or intervals about the circumference. Upon the passage of the electrical current from one contact to the other, suitable pressure being exerted, the two parts of the knife are fused and welded together at such points, substantially as .already'described with respect to the construction shown in Figs. 1, 2 and 3.

It will be understood that the particular manner of welding together the two parts of the knife at isolated oints may be varied to suit dilferent condltions, it being simply necessary that such welding shall be effected at intervals only about the circumference of the knife. Such integral union of the blade and base at intervals only about the circumference of the knife ermits the blade to have such a degree 0 flexibility as it has been found is necessary to enable it to withstand the variation of temperature to which it is subjected in manufacture and in use without cracking or warping.

I claim as my invention:

*1. An annular knife comprising a cupshaped base and a cylindrical blade, the two.

being integrally united at intervals about the circumference to secure the blade and base together While permitting expansion and contraction of the blade independently of the base.

2. An annular knife com rising a stamped cup-shaped base of soft stee and a cylindrlcal knife of high-grade steel, the two being integrally united at intervals about-the circumference to secure the blade and base together while permitting expansion and con graction of the blade independently of the ase.

I 3. An annular knife comprising a stamped cup-shaped base. of. soft steel with a well rounded internal shoulder and a cylindrical knife of high-grade steel, the two being integrally united at intervals about the cir cumference to secure the blade and base together while permitting expanslon and con-.

{)raction of the blade independently of the ase.

This s ecification signed and witnessed this 8th ay of May, A. D., 1907.

' ERNST GUSTAV HOFFMANN. Signed in the resence of AMBROSE OSEEA, -ELLA J. K UGER. 

